A common approach to laying out construction projects includes the use of a transit and a survey rod. Current transit technologies include total stations and robotic total stations allowing for relatively quickly determining the position of the survey rod without the use of separate distance measuring devices and without resorting to manual adjustments of the angle turned by the transit. Rather, the spatial analysis capabilities of the total station allow the location of the survey rod to be determined electronically once detected. The detection of the rod may be provided by optical communication between the total station and a prism arranged on the survey rod.
In use, a total station or robotic total station may be provided with a series of points that can be used to construct a building or arrange electrical conduit, plumbing, or duct work in a building, for example, or to construct other structures such as bridges, roadways, or other projects. In some cases a BIM model may be uploaded to the total station to provide points for layout of a building, components thereof, or for other types of projects. The total station can then be used to repeatedly check locations of the survey rod and as correct locations are identified, survey stakes, paint, pins, or other markings can be made to guide the construction of the facility. For purposes of simplicity, references to total station throughout the specification may include robotic total stations and those without robotic capacity. That is, a reference to a total station should not be construed as excluding robotic total stations.
An accurate layout is dependent, in part, on the relative location of the prism near the top of the rod and the bottom point of the rod. That is, the system may assume that the location of the prism is directly above the location on the ground and, thus, if the prism is in the correct location, the point at the bottom of the rod reflects the correct location on the ground. Accordingly, leveling bubbles are often provided on the rod to assure that the rod is plumb.
The layout of each location is typically done by placing the survey rod in an estimated location and checking the location with the transit. Each time the rod is placed, the rod is plumbed and the location is checked. The transit may be able to tell how far off the rod is such that the correct location can be more closely approached each time. However, the rod may be replaced at a new location and each time the rod is placed it is typically plumbed before the location is checked.